Process for preparation of half-vanadocene compound

ABSTRACT

A process for preparing a half-vanadocene compound, the process comprising reacting chlorine gas with a vanadocene compound represented by the formula (1)
 
Cp 2 VX 2   (1)
 
wherein Cp represents cyclopentadienyl, substituted cyclopentadienyl, indenyl, substituted indenyl, fluorenyl, substituted fluorenyl, benzoindenyl, substituted benzoindenyl, azulenyl or substituted azulenyl, and the two Cp groups may be the same or different, X represents fluorine, chlorine, bromine or iodine and the two X atoms may be the same or different.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a process for preparing ahalf-vanadocene compound and more particularly to a process forpreparing a half-vanadocene compound in a high yield using a chemicallystable vanadocene compound as a starting material.

2. Description of Related Art

A half-vanadocene compound, typically vanadium complex ofcyclopentadiene, is widely used as a catalyst for polymerization ofolefins or diolefins. The half-vanadocene compound exhibits a highactivity as a catalyst for polymerization of butadiene, and is animportant catalyst which is indispensable in organic synthesis.

Examples of the half-vanadocene compound include (C₅H₅)VOCl₂, (C₅H₅)VCl₃and the like. A number of processes are known for preparing suchhalf-vanadocene compounds.

It was reported to prepare (C₅H₅)VOCl₂ by reacting (C₅H₅)V(CO)₄ with amixed gas of oxygen and chlorine (J. Organomet. Chem., No. 319, page C21(1987)). Further reported was a process for preparing (C₅H₅)VOCl₂ byreacting(C₅H₅)V(CO)₄ with oxygen and SOCl₂ (Z. Naturforsch., B: Chem.Sci., No. 53, p. 153 (1998)).

However, these processes pose problems. If purified (C₅H₅)V(CO)₄ is notused as the starting material, the contemplated compound can not beproduced with a high purity in a high yield. Further these processes arenot practical in other respects. (C₅H₅)V(CO)₄ used as the startingmaterial is likely to decompose, and a large amount of toxic carbonmonoxide is required in preparation of the compound. Moreover, a largeamount of toxic carbon monoxide is produced in chlorination of(C₅H₅)V(CO)₄.

A process was reported for preparing (C₅H₅)VOCl₂ by reacting (C₅H₅)₂Vwith (CH₃)₃COOH to give (C₅H₅)VO₂ and treating the obtained compoundwith SOCl₂. (Tr. Khim. Khim. Tekhnol., Vol. 4, p. 32 (1974)). Thisprocess necessitates separation and removal of by-products in the causeof the reaction so that the reaction involves a prolonged reactionprocedure for conversion of an industrial raw material VCl₄ to(C₅H₅)VOCl₂. Thus the process is not practical.

Japanese Unexamined Patent Publications No. 298191/1998 and No.130779/1999 disclose processes for preparing(C₅H₅)VOCl₂ by reactingVOCl₃ with (C₅H₅)MgCl. However, the (C₅H₅)VOCl₂ is produced in a yieldof as low as 25%. Thus the disclosed processes are not practical.

Also reported was a process for preparing (C₅H₅)VCl₃ which comprisesreacting (C₅H₅)V(CO)₄ with SOCl₂ (Z. Anorg. Allg. Chem., No. 423, p. 231(1976)). This process needs (C₅H₅)V(CO)₄ as the raw material and is notpractical.

The above-mentioned publication also discloses a process forpreparing(C₅H₅)VCl₃ which comprises treating (C₅H₅)₂VCl₂ with SOCl₂.However, when purified (C₅H₅)₂VCl₂ is not used as the raw material, ahigh-purity (C₅H₅)VCl₃ would not be produced in a high yield.

As described above, prior art processes for preparing a half-vanadocenecompound are not practical in that the starting compound is likely todecompose and a half-vanadocene compound can not be produced in asufficiently high yield.

BRIEF SUMMARY OF THE INVENTION

An object of the present invention is to provide a process for easilypreparing a half-vanadocene compound with a high purity.

The present inventor carried out research to achieve the foregoingobject and found that a half-vanadocene compound can be produced with ahigh purity in a high yield by reacting chlorine gas with a vanadocenecompound represented by the formula (1)Cp₂VX₂  (1)wherein Cp represents cyclopentadienyl, substituted cyclopentadienyl,indenyl, substituted indenyl, fluorenyl, substituted fluorenyl,benzoindenyl, substituted benzoindenyl, azulenyl or substitutedazulenyl, and the two Cp groups may be the same or different, Xrepresents fluorine, chlorine, bromine or iodine, and the two X atomsmay be the same or different.

The present invention was completed based on the foregoing novel findingand provides the following processes for preparing a half-vanadocenecompound:

-   -   1. A process for preparing a half-vanadocene compound, the        process comprising reacting chlorine gas with a vanadocene        compound represented by the formula (1)        Cp₂VX₂  (1)        wherein Cp represents cyclopentadienyl, substituted        cyclopentadienyl, indenyl, substituted indenyl, fluorenyl,        substituted fluorenyl, benzoindenyl, substituted benzoindenyl,        azulenyl or substituted azulenyl, and the two Cp groups may be        the same or different, X represents fluorine, chlorine, bromine        or iodine and the two X atoms may be the same or different,        either in the presence of at least one member selected from        group consisting of oxygen and water or in the absence of oxygen        and water.    -   2. A process for preparing a half-vanadocene compound according        to item 1, wherein Cp represents cyclopentadienyl;        cyclopentadienyl having 1 to 5 substituents selected from the        group consisting of hydrocarbon groups having 1 to 20 carbon        atoms and silicon-containing hydrocarbon groups having 1 to 20        carbon atoms; indenyl; indenyl having 1 to 6 substituents        selected from the group consisting of hydrocarbon groups having        1 to 20 carbon atoms and silicon-containing hydrocarbon groups        having 1 to 20 carbon atoms; fluorenyl; fluorenyl having 1 to 8        substituents selected from the group consisting of hydrocarbon        groups having 1 to 20 carbon atoms and silicon-containing        hydrocarbon groups having 1 to 20 carbon atoms; benzoindenyl;        benzoindenyl having 1 to 8 substituents selected from the group        consisting of hydrocarbon groups having 1 to 20 carbon atoms and        silicon-containing hydrocarbon groups having 1 to 20 carbon        atoms; azulenyl; or azulenyl having 1 to 7 substituents selected        from the group consisting of hydrocarbon groups having 1 to 20        carbon atoms and silicon-containing hydrocarbon groups having 1        to 20 carbon atoms, and the two Cp groups may be the same or        different.    -   3. A process for preparing a half-vanadocene compound according        to item 1 or 2, wherein Cp represents cyclopentadienyl;        cyclopentadienyl having 1 to 5 substituents selected from the        group consisting of methyl, ethyl, n-propyl, iso-propyl,        n-butyl, iso-butyl, sec-butyl, t-butyl and phenyl; indenyl;        indenyl having 1 to 6 substituents selected from the group        consisting of methyl, ethyl, n-propyl, iso-propyl, n-butyl,        iso-butyl, sec-butyl, t-butyl and phenyl; fluorenyl; fluorenyl        having 1 to 8 substituents selected from the group consisting of        methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl,        sec-butyl, t-butyl and phenyl; benzoindenyl; benzoindenyl having        1 to 8 substituents selected from the group consisting of        methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl,        sec-butyl, t-butyl and phenyl; azulenyl; or azulenyl having 1 to        7 substituents selected from the group consisting of methyl,        ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, sec-butyl,        t-butyl and phenyl, and the two Cp groups may be the same or        different.    -   4. The process for preparing a half-vanadocene compound        according to item 1, 2 or 3, wherein the compound represented by        the formula (1) is selected from the group consisting of        (C₅H₅)₂VF₂, (C₅H₅)₂VCl₂, (C₅H₅)₂VBr₂, (C₅H₅)₂VI₂, (CH₃C₅H₄)₂VF₂,        (CH₃C₅H₄)₂VCl₂, (CH₃C₅H₄)₂VBr₂, (CH₃C₅H₄)₂VI₂,        [1,2-(CH₃)₂C₅H₃]₂VF₂, [1,2-(CH₃)₂C₅H₃]₂VCl₂,        [1,2-(CH₃)₂C₅H₃]₂VBr₂, [1,2-(CH₃)₂C₅H₃]₂VI₂,        [1,3-(CH₃)₂C₅H₃]₂VF₂, [1,3-(CH₃)₂C₅H₃]₂VCl₂,        [1,3-(CH₃)₂C₅H₃]₂VBr₂, [1,3-(CH₃)₂C₅H₃]₂VI₂,        [1,2,3-(CH₃)₃C₅H₂]₂VF₂, [1,2,3-(CH₃)₃C₅H₂]₂VCl₂,        [1,2,3-(CH₃)₃C₅H₂]₂VBr₂, [1,2,3-(CH₃)₃C₅H₂]₂VI₂,        [1,2,4-(CH₃)₃C₅H₂]₂VF₂, [1,2,4-(CH₃)₃C₅H₂]₂VCl₂,        [1,2,4-(CH₃)₃C₅H₂]₂VBr₂, [1,2,4-(CH₃)₃C₅H₂]₂VI₂,        [(CH₃)₄C₅H]₂VF₂, [(CH₃)₄C₅H]₂VCl₂, [(CH₃)₄C₅H]₂VBr₂,        [(CH₃)₄C₅H]₂VI₂, [(CH₃)₅C₅]₂VF₂, [(CH₃)₅C₅]₂VCl₂, [(CH₃)        ₅C₅]₂VBr₂, [(CH₃) ₅C₅]₂VI₂, (1-CH₃-2-C₂H₅C₅H₃)₂VF₂,        (1-CH₃-2-C₂H₅C₅H₃)₂VCl₂, (1-CH₃-2-C₂H₅C₅H₃)₂VBr₂,        (1-CH₃-2-C₂H₅C₅H₃)₂VI₂, (1-CH₃-3-C₂H₅C₅H₃)₂VF₂,        (1-CH₃-3-C₂H₅C₅H₃)₂VCl₂, (1-CH₃-3-C₂H₅C₅H₃)₂VBR₂,        (1-CH₃-3-C₂H₅C₅H₃)₂VI₂, (1-CH₃ -2-n-C₃H₇C₅H₃)₂VF₂,        (1-CH₃-2-n-C₃H₇C₅H₃)₂VCl₂, (1-CH₃-2-n-C₃H₇C₅H₃)₂VBr₂,        (1-CH₃-2-n-C₃H₇C₅H₃)₂VI₂, (1-CH₃-2-iso-C₃H₇C₅H₃)₂VF₂,        (1-CH₃-2-iso-C₃H₇C₅H₃)₂VCl₂, (1-CH₃-2-iso-C₃H₇C₅H₃)₂VBr₂,        (1-CH₃-2-iso-C₃H₇C₅H₃)₂VI₂, (1-CH₃-3-n-C₃H₇C₅H₃)₂VF₂,        (1-CH₃-3-n-C₃H₇C₅H₃)₂VCl₂, (1-CH₃-3-n-C₃H₇C₅H₃)₂VBr₂,        (1-CH₃-3-n-C₃H₇C₅H₃)₂VI₂, (1-CH₃-3-iso-C₃H₇C₅H₃)₂VF₂,        (1-CH₃-3-iso-C₃H₇C₅H₃)₂VCl₂, (1-CH₃-3-iso-C₃H₇C₅H₃)₂VBr₂,        (1-CH₃-3-iso-C₃H₇C₅H₃)₂VI₂, (C₂H₅C₅H₄)₂VF₂, (C₂H₅C₅H₄)₂VCl₂,        (C₂H₅C₅H₄)₂VBr₂, (C₂H₅C₅H₄)₂VI₂, [1,2-(C₂H₅)₂C₅H₃]₂VF₂,        [1,2-(C₂H₅)₂C₅H₃]₂VCl₂, [1,2-(C₂H₅)₂C₅H₃]₂VBr₂,        [1,2-(C₂H₅)₂C₅H₃]₂VI₂, [1,3-(C₂H₅)₂C₅H₃]₂VF₂,        [1,3-(C₂H₅)₂C₅H₃]₂VCl₂, [1,3-(C₂H₅) ₂C₅H₃]₂VBr₂, [1,3-(C₂H₅)        ₂C₅H₃]₂VI₂, [1,2-(n-C₃H₇)₂C₅H₃]₂VF₂, [1,2-(n-C₃H₇)₂C₅H₃]₂VCl₂,        [1,2-(n-C₃H₇)₂C₅H₃]₂VBr₂, [1,2-(n-C₃H₇)₂C₅H₃]₂VI₂,        [1,3-(n-C₃H₇)₂C₅H₃]₂VF₂, [1,3-(n-C₃H₇)₂C₅H₃]₂VCl₂,        [1,3-(n-C₃H₇)₂C₅H₃]₂VBr₂, [1,3-(n-C₃H₇)₂C₅H₃]₂VI₂,        [1,2-(iso-C₃H₇)₂C₅H₃]₂VF₂, [1,2-(iso-C₃H₇)₂C₅H₃]₂VCl₂,        [1,2-(iso-C₃H₇)₂C₅H₃]₂VBr₂, [1,2-(iso-C₃H₇)₂C₅H₃]₂VI₂,        [1,3-(iso-C₃H₇)₂C₅H₃]₂VF₂, [1,3-(iso-C₃H₇)₂C₅H₃]₂VCl₂,        [1,3-(iso-C₃H₇)₂C₅H₃]₂VBr₂, [1,3-(iso-C₃H₇)₂C₅H₃]₂VI₂,        [1,2-(n-C₄H₉)₂C₅H₃]₂VF₂, [1,2-(n-C₄H₉)₂C₅H₃]₂VCl₂,        [1,2-(n-C₄H₉)₂C₅H₃]₂VBr₂, [1,2-(n-C₄H₉)₂C₅H₃]₂VI₂,        [1,3-(n-C₄H₉)₂C₅H₃]₂VF₂, [1,3-(n-C₄H₉)₂C₅H₃]₂VCl₂,        [1,3-(n-C₄H₉)₂C₅H₃]₂VBr₂, [1,3-(n-C₄H₉)₂C₅H₃]₂VI₂,        [1,3-(t-C₄H₉)₂C₅H₃]₂VF₂, [1,3-(t-C₄H₉)₂C₅H₃]₂VCl₂,        [1,3-(t-C₄H₉)₂C₅H₃]₂VBr₂, [1,3-(t-C₄H₉)₂C₅H₃]₂VI₂,        (n-C₅H₁₁C₅H₄)₂VF₂, (n-C₅H₁₁C₅H₄)₂VCl₂, (n-C₅H₁₁C₅H₄)₂VBr₂,        (n-C₅H₁₁C₅H₄)₂Vl₂, (n-C₆H₁₃C₅H₄)₂VF₂, (n-C₆H₁₃C₅H₄)₂VCl₂,        (n-C₆H₁₃C₅H₄)₂VBr₂, (n-C₆H₁₃C₅H₄)₂VI₂, (n-C₈H₁₇C₅H₄)₂VF₂,        (n-C₈H₁₇C₅H₄)₂VCl₂, (n-C₈H₁₇C₅H₄)₂VBr₂, (n-C₈H₁₇C₅H₄)₂VI₂,        (C₆H₅C₅H₄)₂VF₂, (C₆H₅C₅H₄) ₂VCl₂, (C₆H₅C₅H₄)₂VBr₂,        (C₆H₅C₅H₄)₂VI₂, (C₆H₅CH₂C₅H₄)₂VF₂, (C₆H₅CH₂C₅H₄)₂VCl₂,        (C₆H₅CH₂C₅H₄)₂VBr₂, (C₆H₅CH₂C₅H₄)₂VI₂, [(CH₃)₃SiC₅H₄]₂VF₂,        [(CH₃)₃SiC₅H₄]₂VCl₂, [(CH₃)₃SiC₅H₄]₂VBr₂, [(CH₃)₃SiC₅H₄]₂VI₂,        {1,3-[(CH₃)₃Si]₂C₅H₃}₂VF_(2 , {1,3)-[(CH₃)₃Si]₂C₅H₃}₂VCl_(2 , {1,3)-[(CH₃)₃Si]₂C₅H₃}₂VBr_(2 , {1,3)-[(CH₃)₃Si]₂C₅H₃}₂VI_(2 , [(CH)        ₃)₃Si(CH₃)C₅H₃]₂VF₂, [1-(CH₃)₃Si-3-CH₃C₅H₃]₂VCl₂,        [1-(CH₃)₃Si-3-CH₃C₅H₃]₂VBr₂, [1-(CH₃)₃Si-3-CH₃C₅H₃]₂VI₂,        {1,3-[(CH₃)₃Si]₂-4-CH₃C₅H₂}₂VF₂,        {1,3-[(CH₃)₃Si]₂-4-CH₃C₅H₂}₂VCl₂,        {1,3-[(CH₃)₃Si]₂-4-CH₃C₅H₂}₂VBr₂,        {1,3-[(CH₃)₃Si]₂-4-CH₃C₅H₂}₂VI₂, Ind₂VF₂, Ind₂VCl₂, Ind₂VBr₂,        Ind₂VI₂, (2-CH₃Ind)₂VF₂, (2-CH₃Ind)₂VCl₂, (2-CH₃Ind)₂VBr₂,        (2-CH₃Ind)₂VI₂, (2-C₂H₅Ind)₂VF₂, (2-C₂H₅Ind)₂VCl₂,        (2-C₂H₅Ind)₂VBrF₂, (2-C₂H₅Ind)₂VI₂, (2-n-C₃H₇Ind)₂VF₂,        (2-n-C₃H₇Ind)₂VCl₂, (2-n-C₃H₇Ind)₂VBr₂, (2-n-C₃H₇Ind)₂Vl₂,        (2-iso-C₃H₇Ind)₂VF₂, (2-iso-C₃H₇Ind)₂VCl₂, (2-iso-C₃H₇Ind)₂VBr₂,        (2-iso-C₃H₇Ind)₂VI₂, (2-n-C₄H₉Ind)₂VF₂, (2-n-C₄H₉Ind)₂VCl₂,        (2-n-C₄H₉Ind)₂VBr₂, (2-n-C₄H₉Ind)₂VI₂, (2-t-C₄H₉Ind)₂VF₂,        (2-t-C₄H₉Ind)₂VCl₂, (2-t-C₄H₉Ind)₂VBr₂, (2-t-C₄H₉Ind)₂Vl₂,        [2-(CH₃)₃SiInd)]₂VF₂, [2-(CH₃)₃SiInd)]₂VCl₂,        [2-(CH₃)₃SiInd)]₂VBr₂, [2-(CH₃)₃SiInd)]₂VI₂,        [2,4-(CH₃)₂Ind)]₂VF₂, [2,4-(CH₃)₂Ind)]₂VCl₂,        [2,4-(CH₃)₂Ind)]₂VBr₂, [2,4-(CH₃)₂Ind)]₂VI₂,        (2-CH₃-4-C₆H₅Ind)₂VF₂, (2-CH₃-4-C₆H₅Ind) ₂VCl₂,        (2-CH₃-4-C₆H₅Ind)₂VBr₂, (2-CH₃-4-C₆H₅Ind) ₂Vl₂, (H₄Ind)2VF₂,        (H₄Ind)₂VCl₂, (H₄Ind)₂VBr₂, (H₄Ind) ₂VI₂, Flu₂VF₂, Flu₂VCl₂,        Flu₂VBr₂, Flu₂VI₂, (9-CH₃Flu)₂VF₂, (9-CH₃Flu)₂VCl₂,        (9-CH₃Flu)₂VBr₂, (9-CH₃Flu)₂VI₂, (9-C₂H₅Flu)₂VF₂,        (9-C₂H₅Flu)₂VCl₂, (9-C₂H₅Flu)₂VBr₂, (9-C₂H₅Flu)₂VCl₂,        (9-n-C₃H₇Flu)₂VF₂, (9-n-C₃H₇Flu)₂VCl₂, (9-n-C₃H₇Flu)₂VBr₂,        (9-n-C₃H₇Flu) ₂VI₂, (9-iso-C₃H₇Flu) ₂VF₂, (9-iso-C₃H₇Flu)₂VCl₂,        (9-iso-C₃H₇Flu)₂VBr₂, (9-iso-C₃H₇Flu) ₂VI₂, (9-n-C₄H₉Flu)₂VF₂,        (9-n-C₄H₉Flu)₂VCl₂, (9-n-C₄H₉Flu)₂VBr₂, (9-n-C₄H₉Flu)₂Vl₂,        [1,9-(CH₃)₂Flu]₂VF₂, [1,9 -(CH₃)₂Flu]₂VCl₂,        [1,9-(CH₃)₂Flu]₂VBr₂, [1,9-(CH₃)₂Flu]₂VI₂, (H₈Flu)₂VF₂, (H₈Flu)        ₂VCl₂, (H₈Flu)₂VBr₂, (H₈Flu)₂VI₂, Bind₂VF₂, Bind2VCl₂,        Bind₂VBr₂, Bind₂VI₂, (2-CH₃Bind)₂VF₂, (2-CH₃Bind)₂VCl₂,        (2-CH₃Bind)₂VBr₂, (2-CH₃Bind)₂VI₂, (2-C₂H₅Bind)₂VF₂,        (2-C₂H₅Bind)₂VCl₂, (2-C₂H₅Bind)₂VBr₂, (2-C₂H₅Bind)₂VI₂,        (2-n-C₃H₇Bind)₂VF₂, (2-n-C₃H₇Bind)₂VCl₂, (2-n-C₃H₇Bind)₂VBr₂,        (2-n-C₃H₇Bind)₂VI₂, (2-iso-C₃H₇Bind)₂VF₂, (2-iso-C₃H₇Bind)₂VCl₂,        (2-iso-C₃H₇Bind)₂VBr₂, (2-iso-C₃H₇Bind)₂VI₂, (2-n-C₄H₉Bind)        ₂VF₂, (2-n-C₄H₉Bind)₂VCl₂, (2-n-C₄H₉Bind) ₂VBr₂,        (2-n-C₄H₉Bind)₂VI₂, (2-t-C₄H₉Bind) ₂VF₂, (2-t-C₄H₉Bind) ₂VCl₂,        (2-t-C₄H₉Bind)₂VBr₂, (2-t-C₄H₉Bind)₂VI₂, Azu₂VF₂, Azu2VCl₂,        Azu₂VBr₂, Azu₂VI₂, (2-CH₃Azu)₂VF₂, (2-CH₃Azu)₂VCl₂,        (2-CH₃Azu)₂VBr₂, (2-CH₃Azu)₂VI₂, (2-C₂H₅Azu)₂VF₂ ,        (2-C₂H₅Azu)₂VCl₂, (2-C₂H₅Azu)₂VBr₂, (2-C₂H₅Azu)₂VI₂,        (2-n-C₃H₇Azu)₂VF₂, (2-n-C₃H₇Azu)₂VCl₂, (2-n-C₃H₇Azu)₂VBr₂,        (2-n-C₃H₇AZU) ₂VI₂, (2-iso-C₃H₇Azu)₂VF₂, (2-iso-C₃H₇Azu)₂VCl₂,        (2-iso-C₃H₇Azu)₂VBr₂, (2-iso-C₃H₇Azu)_(2VI) ₂,        (4,8-(CH₃)₂Azu)₂VF₂, (4,8-(CH₃)₂Azu) ₂VCl₂,        (4,8-(CH₃)₂Azu)₂VBr₂, (4,8-(CH₃) ₂Azu)₂VI₂,        (2,4,8-(CH₃)₃Azu)₂VF₂, (2,4,8-(CH₃)₃Azu)₂VCl₂,        (2,4,8-(CH₃)₃Azu)₂VBr₂, (2,4,8-(CH₃)₃Azu)₂VI₂,        [2-iso-C₃H₇-4,8-(CH₃)₂Azu]₂VF₂, [2-iso-C₃H₇-4,8-(CH₃)₂Azu]₂VCl₂,        [2-iso-C₃H₇-4,8-(CH₃)₂Azu]₂VBr₂ and        [2-iso-C₃H₇-4,8-(CH₃)₂Azu]₂VI₂, wherein Ind represents indenyl,        Flu represents fluorenyl, Bind represents benzoindenyl, Azu        represents azulenyl, H₄Ind represents the following group (6),        and H₈Flu represents the following group (7).    -   5. The process for preparing a half-vanadocene compound        according to any of items 1 to 4, wherein the vanadocene        compound represented by the formula (1) is reacted with chlorine        gas in the presence of at least one member selected from the        group consisting of oxygen and water.    -   6. The process for preparing a half-vanadocene compound        according to item 5, wherein the half-vanadocene compound to be        obtained is a compound represented by the formula (3)        CpVOCl₂  (3)        wherein Cp represents cyclopentadienyl, substituted        cyclopentadienyl, indenyl, substituted indenyl, fluorenyl,        substituted fluorenyl, benzoindenyl, substituted benzoindenyl,        azulenyl or substituted azulenyl.    -   7. The process for preparing a half-vanadocene compound        according any of items 1 to 4, wherein the vanadocene compound        represented by the formula (1) is reacted with chlorine gas in        the absence of oxygen and water.    -   8. The process for preparing a half-vanadocene compound        according to item 7, wherein the half-vanadocene compound to be        obtained is a compound represented by the formula (2)        CPVCl₃  (2)        wherein Cp represents cyclopentadienyl, substituted        cyclopentadienyl, indenyl, substituted indenyl, fluorenyl,        substituted fluorenyl, benzoindenyl, substituted benzoindenyl,        azulenyl or substituted azulenyl.    -   9. A process for preparing a half-vanadocene compound according        to any of items of 1 to 8, wherein the process further comprises        the step of reacting a vanadium compound represented by the        formula (4)        VX₄  (4)        wherein X represents fluorine, chlorine, bromine or iodine, and        the four X atoms may be the same or different with at least one        of alkali metal compounds represented by the formula (5)        CpM  (5)        wherein Cp represents cyclopentadienyl, substituted        cyclopentadienyl, indenyl, substituted indenyl, fluorenyl,        substituted fluorenyl, benzoindenyl, substituted benzoindenyl,        azulenyl or substituted azulenyl, M represents lithium, sodium,        potassium, rubidium or cesium to obtain a vanadocene compound        represented by the formula (1)        Cp₂VX₂  (1)        wherein Cp and X are as defined in claim 1.

According to the invention of item 1, a half-vanadocene compound can beeasily prepared with a high purity in a high yield by using a vanadocenecompound of the formula (1) (Cp₂VX₂) which is chemically stable, and byreacting the vanadocene compound of the formula (1) with chlorine gas.

The process of the invention is simplified and the reaction conditionscan be easily controlled and therefore the process gives ahalf-vanadocene compound on a mass-production basis.

As described above, a high purity half-vanadocene compound can beproduced on a mass-production basis according to the producing processof the invention, and the obtained half-vanadocene compound can beprovided in various fields such as a catalyst to be used in organicsynthesis (especially a catalyst for polymerization of olefins ordiolefins).

According to the invention of item 5, a half-vanadocene compoundrepresented by the formula CpVOCl₂ can be easily prepared with a highpurity in a high yield by reacting the vanadocene compound representedby the formula (1) with chlorine gas in the presence of oxygen and/orwater.

According to the invention of item 7, a half-vanadocene compoundrepresented by the formula CpVCl₃ can be easily prepared with a highpurity in a high yield by reacting the vanadocene compound representedby the formula (1) with chlorine in the absence of oxygen and water.

In the process of the invention, it is preferable that a vanadiumcompound (VX₄) is reacted with an alkali metal compound (CpM) to give avanadocene compound (Cp₂VX₂) as set forth in item 9. In this reaction,an alkali metal salt (MX) is produced as a by-product, but does notinterfere with the chlorination of vanadocene compound (Cp₂VX₂) withchlorine gas in the next step. Thus, the obtained vanadocene compoundrepresented by the formula (1) (Cp₂VX₂) can be reacted, without itspurification, with chlorine gas, whereby the producing process can besimplified.

In the process of this invention, the vanadium compound (VX₄) generallyused as an industrial raw material can be used as the raw material, andtherefore the vanadocene compound (Cp₂VX₂) and the half-vanadocenecompound prepared therefrom can be mass-produced. Furthermore thereaction conditions can be easily controlled in the reaction between thevanadocene compound (Cp₂VX₂) and chlorine gas. Therefore ahalf-vanadocene compound can be easily prepared with a high purity in ahigh yield.

DETAILED DESCRIPTION OF THE INVENTION

The process for preparing a half-vanadocene compound according to theinvention includes a step of chlorinating a vanadocene compoundrepresented by the formula (1)Cp₂VX₂  (1)wherein Cp and X are as defined above.

In the process of the invention, especially, chlorine gas is used forchlorination.

Vanadocene Compound

X in the formula (1) represents fluorine, chlorine, bromine or iodine,and the two X atoms may be the same or different. X is preferablychlorine or bromine, more preferably chlorine.

Cp in the formula (1) represents a group having a cyclopentadienylskeleton. More specifically, Cp represents cyclopentadienyl, substitutedcyclopentadienyl, indenyl, substituted indenyl, fluorenyl, substitutedfluorenyl, benzoindenyl, substituted benzoindenyl, azulenyl orsubstituted azulenyl, and the two Cp groups may be the same ordifferent. Cp is preferably cyclopentadienyl or substitutedcyclopentadienyl, and more preferably cyclopentadienyl.

When Cp in the formula (1) is a group having one or more substituents,preferred substituents are selected from the group consisting ofhydrocarbon groups having 1 to 20 carbon atoms and silicon-containinghydrocarbon groups having 1 to 20 carbon atoms.

Preferred examples of hydrocarbon groups having 1 to 20 carbon atomsinclude:

-   -   alkyl groups having 1 to 20 carbon atoms, especially alkyl        groups having 1 to 8 carbon atoms, such as methyl, ethyl,        n-propyl, iso-propyl, n-butyl, iso-butyl, sec-butyl, t-butyl,        n-pentyl, iso-pentyl, neo-pentyl, tert-pentyl, n-hexyl,        iso-hexyl, octyl and like;    -   aralkyl groups, especially phenyl-C₁-C₄ alkyl groups, such as        benzyl;    -   aryl groups having 6 to 20, especially 6 to 12, carbon atoms        including phenyl optionally substituted with 1 to 3 C₁-C₄ alkyl        groups, such as toluyl, phenyl, 2,6-dimethylphenyl,        2,6-di-iso-propyl-phenyl, mesityl, as well as naphthyl and the        like; adamantyl and the like.

Among the silicon-containing hydrocarbon groups having 1 to 20 carbonatoms, preferred are hydrocarbon groups having 3 to 12 carbon atoms, and1 or 2 silicon atoms such as trimethylsilyl, trimethylsilylmethyl,bis(trimethylsilyl)methyl and the like.

Among the foregoing substituents, methyl, ethyl, n-propyl, iso-propyl,n-butyl, iso-butyl, sec-butyl, t-butyl and phenyl are preferred. Methyl,iso-propyl and t-butyl are more preferred.

The substituted cyclopentadienyl group may have 1 to 5 substituents,preferably 1 or 2 substituents. The substituted indenyl group may have 1to 6 substituents, preferably 1 to 3 substituents. The substitutedfluorenyl group may have 1 to 8 substituents, preferably 1 or 2substituents. The substituted benzoindenyl group may have 1 to 8substituents, preferably 1 or 2 substituents. The substituted azulenylgroup may have 1 to 7 substituents, preferably 1 or 2 substituents.

Specific examples of the substituted cyclopentadienyl group aremethylcyclopentadienyl, 1,2-dimethylcyclopentadienyl,1,3-dimethylcyclopentadienyl, 1,2,3-trimethylcyclopentadienyl,1,2,4-trimethylcyclopentadienyl, tetramethylcyclopentadienyl,pentamethylcyclopentadienyl, 1-methyl-2-ethylcyclopentadienyl,1-methyl-3-ethylcyclopentadienyl, 1-methyl-2-propylcyclopentadienyl,1-methyl-3-propylcyclopentadienyl, ethylcyclopentadienyl,1,2-diethylcyclopentadienyl, 1,3-diethylcyclopentadienyl,1,2-di-n-propylcyclopentadienyl, 1,3-di-n-propylcyclopentadienyl,1,2-di-iso-propylcyclopentadienyl, 1,3-di-iso-propylcyclopentadienyl,1,2-di-n-butylcyclopentadienyl, 1,3-di-n-butylcyclopentadienyl,1,3-di-t-butylcyclopentadienyl, n-pentylcyclopentadienyl,n-hexylcyclopentadienyl, n-octylcyclopentadienyl,phenylcyclopentadienyl, benzylcyclopentadienyl,trimethylsilylcyclopentadienyl, 1,3-bis(trimethylsilyl)cyclopentadienyl,trimethylsilylmethylcyclopentadienyl,bis(trimethylsilyl)methylcyclopentadienyl, etc.

Among them, methylcyclopentadienyl, 1,2-dimethylcyclopentadienyl,1,3-dimethylcyclopentadienyl, 1,2,3-trimethylcyclopentadienyl,1,2,4-trimethylcyclopentadienyl, tetramethylcyclopentadienyl.,pentamethylcyclopentadienyl and ethylcyclopentadienyl are preferred.methylcyclopentadienyl is more preferred.

Specific examples of the substituted indenyl group are 2-methylindenyl,2-ethylindenyl, 2-n-propylindenyl, 2-iso-propylindenyl,2-n-butylindenyl, 2-t-butylindenyl, 2-trimethylsilylindenyl,2,4-dimethylindenyl, 2-methyl-4-phenylindenyl, tetrahydroindenyl, etc.Among them, 2-methylindenyl, 2-iso-propylindenyl, 2-t-butylindenyl andtetrahydroindenyl are preferred. 2-methylindenyl and tetrahydroindenylare more preferred.

Specific examples of the substituted fluorenyl group are9-methylfluorenyl, 9-ethylfluorenyl, 9-n-propylfluorenyl,9-iso-propylfluorenyl, 9-n-butylfluorenyl, 9-methyl-1-methylfluorenyl,octahydrofluorenyl, etc. Among them, 9-methylfluorenyl,9-iso-propylfluorenyl and octahydrofluorenyl are preferred.9-methylfluorenyl and octahydrofluorenyl are more preferred.

Preferred examples of the substituted benzoindenyl group are2-methylbenzoindenyl, 2-ethylbenzoindenyl, 2-n-propylbenzoindenyl,2-iso-propylbenzoindenyl, 2-n-butylbenzoindenyl, 2-t-butylbenzoindenyl,etc. Among them, 2-methylbenzoindenyl, 2-iso-propylbenzoindenyl and2-t-butylbenzoindenyl are preferred. 2-methylbenzoindenyl is morepreferred.

Preferred examples of the substituted azulenyl group are2-methylazulenyl, 2-ethylazulenyl, 2-n-propylazulenyl,2-iso-propylazulenyl, 4,8-dimethylazulenyl, 2,4,8-trimethylazulenyl,4,8-dimethyl-2-iso-propylazulenyl, etc. Among them, 2-methylazulenyl and2-iso-propylazulenyl are preferred and 2-methylazulenyl is morepreferred.

In view of the above, examples of preferable vanadocene compoundsinclude (C₅H₅)₂VF₂, (C₅H₅)₂VCl₂, (C₅H₅)₂VBr₂, (C₅H₅)₂VI₂, (CH₃C₅H₄)₂VF₂,(CH₃C₅H₄)₂VCl₂, (CH₃C₅H₄)₂VBr₂, (CH₃C₅H₄)₂VI₂, [1,2-(CH₃)₂C₅H₃]₂VF₂,[1,2-(CH₃)₂C₅H₃]₂VCl₂, [1,2-(CH₃)₂C₅H₃]₂VBr₂, [1,2-(CH₃)₂C₅H₃]₂VI₂,[1,3-(CH₃)₂C₅H₃]₂VF₂, [1,3-(CH₃)₂C₅H₃]₂VCl₂, [1,3-(CH₃)₂C₅H₃]₂VBr₂,[1,3-(CH₃)₂C₅H₃]₂VI₂, [1,2,3-(CH₃)₃C₅H₂]₂VF₂, [1,3-(CH₃)₃C₅H₂]₂VCl₂,[1,2,3-(CH₃)₃C₅H₂]₂VBr₂, [1,2,3-(CH₃)₃C₅H₂]₂VI₂, [1,2,4-(CH₃)₃C₅H₂]₂VF₂,[1,2,4-(CH₃)₃C₅H₂]₂VCl₂, [1,2,4-(CH₃)₃C₅H₂]₂VBr₂,[1,2,4-(CH₃)₃C₅H₂]₂VI₂, [(CH₃)₄C₅H]₂VF₂, [(CH₃)₄C₅H]₂VCl₂,[(CH₃)₄C₅H]₂VBr₂, [(CH₃)₄C₅H]₂VI₂, [(CH₃)₅C₅]₂VF₂, [(CH₃)₅C₅]₂VCl₂,[(CH₃)₅C₅]₂VBr₂, (1-CH₃-2-C₂H₅C₅H₃)₂VI₂, (1-CH₃-2-C₂H₅C₅H₃)₂VF₂,(1-CH₃-2-C₂H₅C₅H₃)₂VCl₂, (1-CH₃-2-C₂H₅C₅H₃)₂VBr₂,(1-CH₃-2-C₂H₅C₅H₃)₂VI₂, (1-CH₃-3-C₂H₅C₅H₃)₂VF₂, (1-CH₃-3-C₂H₅C₅H₃)₂VCl₂,(1-CH₃-3-C₂H₅C₅H₃)₂VBr₂, (1-CH₃-3-C₂H₅C₅H₃)₂VI₂,(1-CH₃-2-n-C₃H₇C₅H₃)₂VF₂, (1-CH₃-2-n-C₃H₇C₅H₃₎ ₂VCl₂,(1-CH₃-2-n-C₃H₇C₅H₃)₂VBr₂, (1-CH₃-2-n-C₃H₇C₅H₃) ₂VBr₂,(1-CH₃-2-n-C₃H₇C₅H₃)₂VI₂, (1-CH₃-2-iso-C₃H₇C₅H₃)₂VF₂,(1-CH₃-2-iso-C₃H₇C₅H₃)₂VCl₂, (1-CH₃-2-iso-C₃H₇C₅H₃)₂VBr₂,(1-CH₃-2-iso-C₃H₇C₅H₃)₂VI₂, (1-CH₃-3-n-C₃H₇C₅H₃) ₂VF₂,(1-CH₃-3-n-C₃H₇C₅H₃)₂VCl₂, (1-CH₃-3-n-C₃H₇C₅H₃)₂VBr₂,(1-CH₃-3-n-C₃H₇C₅H₃)₂VI₂, (1-CH₃-3-iso-C₃H₇C₅H₃)₂VF₂,(1-CH₃-iso-C₃H₇C₅H₃)₂VCl₂, (1-CH₃-3-iso-C₃H₇C₅H₃)₂VBr₂,(1-CH₃-3-iso-C₃H₇C₅H₃)₂Vl₂, (C₂H₅C₅H₄)₂VF₂(C₂H₅C₅H₄)₂VCl₂(C₂H₅C₅H₄)₂VBr₂(C₂H₅C₅H₄)₂VI₂, [1,2-(C₂H₅)₂C₅H₃]₂VF₂,[1,2-(C₂H₅)₂C₅H₃]₂VCl₂, [1,2-(C₂H₅)₂C₅H₃]₂VBr₂, [1,2-(C₂H₅)₂C₅H₃]₂VI₂,[1,3-(C₂H₅)₂C₅H₃]₂VF₂, [1,3-(C₂H₅)₂C₅H₃] ₂VCl₂, [1,3-(C₂H₅)₂C₅H₃]₂VBr₂,[1,3-(C₂H₅)₂C₅H₃]₂VI₂, [1,2-(n-C₃H₇)₂C₅H₃]₂VF₂,[1,2-(n-C₃H₇)₂C₅H₃]₂VCl₂, [1,2-(n-C₃H₇)₂C₅H₃]₂VBr₂,[1,2-(n-C₃H₇)₂C₅H₃]₂VI₂, [1,3-(n-C₃H₇)₂C₅H₃]₂VF₂,[1,3-(n-C₃H₇)₂C₅H₃]₂VCl₂, [1,3-(n-C₃H₇)₂C₅H₃]₂VBr₂,[1,3-(n-C₃H₇)₂C₅H₃]₂VI₂, [1,2-(iso-C₃H₇)₂C₅H₃]₂VF₂,[1,2-(iso-C₃H₇)₂C₅H₃]₂VCl₂, [1,2-(iso-C₃H₇)₂C₅H₃]₂VBr₂,[1,2-(iso-C₃H₇)₂C₅H₃]₂VI₂, [1,3-(iso-C₃H₇)₂C₅H₃]₂VF₂,[1,3-(iso-C₃H₇)₂C₅H₃]₂VCl₂, [1,3-(iso-C₃H₇)₂C₅H₃]₂VBr₂,[1,3-(iso-C₃H₇)₂C₅H₃]₂VI₂, [1,2-(n-C₄H₉)₂C₅H₃]₂VF₂,[1,2-(n-C₄H₉)₂C₅H₃]₂VCl₂, [1,2-(n-C₄H₉)₂C₅H₃]₂VBr₂,[1,2-(n-C₄H₉)₂C₅H₃]₂VI₂, [1,3-(n-C₄H₉)₂C₅H₃]₂VF₂,[1,3-(n-C₄H₉)₂C₅H₃]₂VCl₂, [1,3-(n-C₄H₉)₂C₅H₃]₂VBr₂,[1,3(n-C₄H₉)₂C₅H₃]₂VI₂, [1,3-(t-C₄H₉)₂C₅H₃]₂VF₂,[1,3-(t-C₄H₉)₂C₅H₃]₂VCl₂, [1,3(t-C₄H₉)₂C₅H₃]₂VBr₂,[1,3-(t-C₄H₉)₂C₅H₃]₂VI₂, (n-C₅H₁₁C₅H₄)₂VF₂, (n-C₅H₁₁C₅H₄)₂VCl₂,(n-C₅H₁₁C₅H₄)₂VBr₂, (n-C₅H₄)₂VI₂, (n-C₆H₁₃C₅H₄)₂VF₂, (n-C₆H₁₃C₅H₄)₂VCl₂,(n-C₆H₁₃C₅H₄)₂VBr₂, (n-C₆H₁₃C₅H₄)₂VI₂, (n-C₈H₁₇C₅H₄)₂VF₂,(n-C₈H₁₇C₅H₄)₂VCl₂, (n-C₈H₁₇C₅H₄)₂VBr₂, (n-C₈H₁₇C₅H₄)₂VI₂,(C₆H₅C₅H₄)₂VF₂, (C₆H₅C₅H₄)₂VCl₂, (C₆H₅C₅H₄)₂VBr₂, (C₆H₅C₅H₄)₂VI₂,(C₆H₅CH₂C₅H₄)₂VF₂, (C₆H₅C₅H₄)₂VCl₂, (C₆H₅CH₂C₅H₄)₂VBr₂,(C₆H₅CH₂C₅H₄)₂VI₂, [(CH₃)₃SiC₅H₄]₂VF₂, [(CH₃)₃SiC₅H₄]₂VCl₂,[(CH₃)₃SiC₅H₄]₂VBr₂, [(CH₃)₃SiC₅H₄]₂Vl₂, {1,3-[(CH₃)₃Si]₂C₅H₃}₂VF₂,{1,3-[(CH₃)₃Si]₂C₅H_(3}) ₂VCl₂, {1,3-[(CH₃)₃Si]₂C₅H₃}₂VBr₂,{1,3-[(CH₃)₃Si]₂C₅H_(3}) ₂VI₂, [(CH₃)₃Si(CH₃)C₅H₃]₂VF₂[1-(CH₃)₃Si-3-CH₃C₅H₃]₂VCl₂, [1-(CH₃)₃Si-3-CH₃C₅H₃]₂VBr₂,[1-(CH₃)₃Si-3-CH₃C₅H₃]₂VI₂, {1,3-[(CH₃)₃Si]₂-4-CH₃C₅H₂}₂VF₂{1,3-[(CH₃)₃Si]₂-4-CH₃C₅H₂}₂VCl₂, {1,3-[(CH₃)₃Si]₂-4-CH₃C₅H₂}₂VBr₂,{1,3-[(CH₃)₃Si]₂-4-CH₃C₅H₂}₂VI₂, Ind₂VF₂, Ind₂VCl₂, Ind₂VBr₂, Ind₂VI₂,(2-CH₃Ind)₂VF₂, (2-CH₃Ind)₂VCl₂, (2-CH₃Ind)₂VBr₂, (2-CH₃Ind)₂VI₂,(2-C₂H₅Ind)₂VF₂, (2-C₂H₅Ind)₂VCl₂, (2-C₂H₅Ind)₂VBr₂, (2-C₂H₅Ind)₂VI₂,(2-n-C₃H₇Ind)₂VF₂, (2-n-C₃H₇Ind)₂VCl₂, (2-n-C₃H₇Ind)₂VCl₂,(2-n-C₃H₇Ind)₂VBr₂, (2-n-C₃H₇Ind)₂VI₂, (2-iso-C₃H₇Ind)₂VF₂,(2-iso-C₃H₇Ind)₂VCl₂, (2-iso-C₃H₇Ind)₂VBr₂, (2-iso-C₃H₇Ind)₂VI₂,(2-n-C₄H₉Ind)₂VF₂, (2-n-C₄H₉Ind)₂VCl₂, (2-n-C₄H₉Ind)₂VBr₂,(2-n-C₄H₉Ind)₂VI₂, (2-t-C₄H₉Ind)₂VF₂, (2-t-C₄H₉Ind)₂VCl₂,(2-t-C₄H₉Ind)₂VBr₂, (2-t-C₄H₉Ind)₂VI₂, [2-(CH₃)₃SiInd)]₂VF₂,[2-(CH₃)₃SiInd)]₂VCl₂, [2-(CH₃)₃SiInd)]₂VBr₂[2-(CH₃)₃SiInd)]₂VI₂,[2,4-(CH₃)₂Ind)]₂VF₂, [2,4-(CH₃)₂Ind)]₂VCl₂, [2,4-(CH₃)₂Ind)]₂VBr₂,[2,4-(CH₃)₂Ind)]₂VI₂, (2-CH₃-4-C₆H₅Ind)₂VF₂, (2-CH₃-4-C₆H₅Ind)₂VCl₂,(2-CH₃-4-C₆H₅Ind)₂VBr₂, (2-CH₃-4-C₆H₅Ind)₂VI₂, (H₄Ind)₂VF₂,(H₄Ind)₂VCl₂, (H₄Ind)₂VBr₂, (H₄Ind)₂VI₂, Flu₂VF₂, Flu₂VCl₂, Flu₂VBr₂,Flu₂VI₂, (9-CH₃Flu)₂VF₂, (9-CH₃Flu)₂VCl₂, (9-CH₃Flu)₂VBr₂,(9-CH₃Flu)₂VI₂, (9-C₂H₅Flu)₂VF₂, (9-C₂H₅Flu)₂VCl₂, (9-C₂H₅Flu)₂VBr₂,(9-C₂H₅Flu)₂VI₂, (9-n-C₃H₇Flu)₂VF₂, (9-n-C₃H₇Flu)₂VCl₂,(9-n-C₃H₇Flu)₂VBr₂,(9-n-C₃H₇Flu)₂VI₂, (9-iso-C₃H₇Flu)₂VF₂,(9-iso-C₃H₇Flu)₂VCl₂, (9-iso-C₃H₇Flu)₂VBr₂, (9-iso-C₃H₇Flu)₂VI₂,(9-n-C₄H₉Flu)₂VF₂, (9-n-C₄H₉Flu)₂VCl₂, (9-n-C₄H₉Flu)₂VBr₂,(9-n-C₄H₉Flu)₂VI₂, [1,9-(CH₃)₂Flu]₂VF₂, [1,9-(CH₃)₂Flu]₂VCl₂,[1,9-(CH₃)₂Flu]₂VBr₂, [1,9-(CH₃)₂Flu]₂VI₂, (H₈Flu)₂VF₂, (H₈Flu)₂VCl₂,(H₈Flu)₂VBr₂, (H₈Flu)₂VI₂, Bind₂VF₂, Bind₂VCl₂, Bind₂VBr₂, Bind₂VI₂,(2-CH₃Bind)₂VF₂, (2-CH₃Bind)₂VCl₂, (2-CH₃Bind)₂VBr₂, (2-CH₃Bind)₂VI₂,(2-C₂H₅Bind)₂VF₂, (2-C₂H₅Bind)₂VCl₂, (2-C₂H₅Bind)₂VBr₂,(2-C₂H₅Bind)₂VI₂, (2-n-C₃H₇Bind)₂VF₂, (2-n-C₃H₇Bind)₂VCl₂,(2-n-C₃H₇Bind)₂VBr₂, (2-n-C₃H₇Bind)₂Vl₂, (2-iso-C₃H₇Bind)₂VF₂,(2-iso-C₃H₇Bind)₂VCl₂, (2-iso-C₃H₇Bind)₂VBr₂, (2-iso-C₃H₇Bind)₂VI₂,(2-n-C₄H₉Bind)₂VF₂, (2-n-C₄H₉Bind)₂VCl₂, (2-n-C₄H₉Bind)₂VBr₂,(2-n-C₄H₉Bind)₂Vl₂, (2-t-C₄H₉Bind)₂VF₂, (2-t-C₄H₉Bind)₂VCl₂,(2-t-C₄H₉Bind)₂VBr₂, (2-t-C₄H₉Bind)₂VI₂, Azu₂VF₂, Azu₂VCl₂, Azu₂VBr₂,Azu₂VI₂, (2-CH₃Azu)₂VF₂, (2-CH₃Azu)₂VCl₂, (2-CH₃Azu)₂VBr₂,(2-CH₃Azu)₂VI₂, (2-C₂H₅Azu)₂VF₂, (2-C₂H₅Azu)₂VCl₂, (2-C₂H₅Azu)₂VBr₂,(2-C₂H₅Azu)₂VI₂, (2-n-C₃H₇Azu)₂VF₂, (2-n-C₃H₇Azu)₂VCl₂,(2-n-C₃H₇Azu)₂VBr₂, (2-n-C₃H₇Azu)₂VI₂, (2-iso-C₃H₇Azu)₂VF₂,(2-iso-C₃H₇Azu)₂VCl₂, (2-iso-C₃H₇Azu)₂VBr₂, (2-iso-C₃H₇Azu)₂VI₂,(4,8-(CH₃)₂Azu)₂VF₂, (4,8-(CH₃)₂Azu)₂VCl₂, (4,8-(CH₃)₂Azu)₂VBr₂,(4,8-(CH₃)₂Azu)₂VI₂, (2,4,8-(CH₃)₃Azu)₂VF₂, (2,4,8-(CH₃)₃Azu)₂VCl₂,(2,4,8-(CH₃)₃Azu)₂VBr₂, (2,4,8-(CH₃)₃Azu)₂VI₂,[2-iso-C₃H₇-4,8-(CH₃)₂Azu]₂VF₂, [2-iso-C₃H₇-4,8-(CH₃)₂Azu]₂VCl₂,[2-iso-C₃H₇-4,8-(CH₃)₂Azu]₂VBr₂, and [2-iso-C₃H₇-4,8-(CH₃)₂Azu]₂VI₂.

In the above formulas, Ind represents indenyl, Flu represents fluorenyl,Bind represents benzoindenyl, Azu represents azulenyl, H₄Ind representsthe following group

and H₈Flu represents the following group. (7).

More preferred are (C₅H₅)₂VCl₂, (C₅H₅)₂VBr₂, (CH₃C₅H₄)₂VCl₂,(CH₃C₅H₄)₂VBr₂, [1,2-(CH₃)₂C₅H₃]₂VCl₂, [1,2-(CH₃)₂C₅H₃]₂VBr₂,[1,3-(CH₃)₂C₅H₃]₂VCl₂, [1,3-(CH₃)₂C₅H₃]₂VBr₂, [1,2,3-(CH₃)₃C₅H₂]₂VCl₂,[1,2,3-(CH₃)₃C₅H₂]₂VBr₂, [1,2,4-(CH₃)₃C₅H₂]₂VCl₂,[1,2,4-(CH₃)₃C₅H₂]₂VBr₂, [(CH₃)₄C₅H]₂VCl₂, [(CH₃)₄C₅]₂VBr₂,[(CH₃)₅C₅]₂VCl₂, [(CH₃)₅C₅]₂VBr₂, (1-CH₃-2-C₂H₅C₅H₃)₂VCl₂,(1-CH₃-2-C₂H₅C₅H₃)₂VBr₂, (1-CH₃-3-C₂H₅C₅H₃)₂VCl₂,(1-CH₃-3-C₂H₅C₅H₃)₂VBr₂, (1-CH₃-2-C₃H₇C₅H₃)₂VCl₂,(1-CH₃-2-C₃H₇C₅H₃)₂VBr₂, (1-CH₃-2-n-C₃H₇C₅H₃)₂VCl₂,(1-CH₃-2-n-C₃H₇C₅H₃)₂VBr₂, (1-CH₃-3-iso-C₃H₇C₅H₃)₂VCl₂,(1-CH₃-3-iso-C₃H₇C₅H₃)₂VBr₂, (C₂H₅C₅H₄)₂VCl₂, (C₂H₅C₅H₄)₂VBr₂,[1,2-(C₂H₅)₂C₅H₃]₂VCl₂, [1,2-(C₂H₅)₂C₅H₃]₂VBr₂, [1,3-(C₂H₅)₂C₅H₃]₂VCl₂,[1,3-(C₂H₅)₂C₅H₃]₂VBr₂, [1,2-(n-C₃H₇)₂C₅H₃]₂VCl₂,[1,2-(n-C₃H₇)₂C₅H₃]₂VBr₂, [1,3-(n-C₃H₇)₂C₅H₃]₂VCl₂,[1,3-(n-C₃H₇)₂C₅H₃]₂VBr₂, [1,2-(iso-C₃H₇)₂C₅H₃]₂VCl₂,[1,2-(iso-C₃H₇)₂C₅H₃]₂VBr₂, [1,3-(iso-C₃H₇)₂C₅H₃]₂VCl₂,[1,3-(iso-C₃H₇)₂C₅H₃]₂VBr₂, [1,2-(n-C₄H₉)₂C₅H₃]₂VCl₂,[1,2-(n-C₄H₉)₂C₅H₃]₂VBr₂, [1,3-(n-C₄H₉)₂C₅H₃]₂VCl₂,[1,3-(n-C₄H₉)₂C₅H₃]₂VBr₂, [1,3-(t-C₄H₉)₂C₅H₃]₂VCl₂,[1,3-(t-C₄H₉)₂C₅H₃]₂VBr₂, (n-C₅H₁₁C₅H₄)₂VCl₂, (n-C₅H₁₁C₅H₄)₂VBr₂,(n-C₆H₁₃C₅H₄)₂VCl₂, (n-C₆H₁₃C₅H₄)₂VBr₂, (n-C₈H₁₇C₅H₄)₂VCl₂,(n-C₈H₁₇C₅H₄)₂VBr₂, (C₆H₅C₅H₄)₂VCl₂, (C₆H₅C₅H₄)₂VBr₂,(C₆H₅CH₂C₅H₄)₂VCl₂, (C₆H₅CH₂C₅H₄)₂VBr₂, [(CH₃)₃SiC₅H₄]₂VCl₂,[(CH₃)₃SiC₅H₄]₂VBr₂, {1,3-[(CH₃)₃Si]₂C₅H₃}₂VCl₂,{1,3-[(CH₃)₃Si]₂C₅H₃}₂VBr₂, [1-(CH₃)₃Si-3-CH₃C₅H₃]₂VCl₂,[1-(CH₃)₃Si-3-CH₃C₅H₃]₂VBr₂, {1,3-[(CH₃)₃Si]₂ -4-CH₃C₅H₂}₂VCl₂, and{1,3-[(CH₃)₃Si]₂-4-CH₃C₅H₂} ₂VBr₂. Still more preferred is (C₅H₅)₂VCl₂.

Process for Preparing Vanadocene Compound (CP₂VX₂)

The vanadocene compound represented by the formula (1) (Cp₂VX₂) ispreferably prepared according to a reaction scheme (I) shown belowVX₄+2CpM→Cp₂VX₂+2MX  (I)

-   -   (4) (5) (1)        using a vanadium compound represented by the formula (4)        VX₄  (4)        wherein X is as defined above and an alkali metal compound        represented by the formula (5)        CpM  (5)        wherein Cp and M are as defined above.

Since the alkali metal salt (MX) is produced as a by-product in thereaction scheme (I), the obtained vanadocene compound (Cp₂VX₂) containsthe alkali metal salt (MX) as impurity. However, the alkali metal salt(MX) does not hinder the chlorination reaction of the vanadocenecompound (Cp₂VX₂) with chlorine gas, which is a feature of theinvention. For this reason, the vanadocene compound (Cp₂VX₂) prepared bythe reaction scheme (I) can be used in the invention withoutpurification.

In view of the above, the purification of vanadocene compound (Cp₂VX₂)can be omitted in the process of the invention, whereby the process canbe simplified and the costs can be lowered. In addition, the vanadiumcompound (VX₄) generally used as an industrial raw material can be usedas the raw material, therefore the vanadocene compound (Cp₂VX₂) and thehalf-vanadocene compound prepared therefrom can be mass-produced.

In the present invention, preferably the vanadium compound representedby the formula (4) (VX₄) is reacted with an alkali metal compoundrepresented by the formula (5) (CpM) to give a vanadocene compound(Cp₂VX₂). Described below is the process for preparing the vanadocenecompound of the formula (1) (Cp₂VX₂) according to the reaction scheme(I).

In the formula (4), X represents fluorine, chlorine, bromine or iodine,and four X atoms may be the same or different. The X atoms may be thoseconstituting the contemplated vanadocene compound of the formula (1).When two X atoms in the contemplated vanadocene compound of the formula(1) are different from each other, two kinds of vanadium compoundshaving different X atoms are used as mixed.

Examples of the vanadium compound (VX₄) are vanadium tetrafluoride,vanadium tetrachloride, vanadium tetrabromide, vanadium tetraiodide andthe like. Among them, vanadium tetrachloride and vanadium tetrabromideare preferred, and vanadium tetrachloride is more preferred.

The vanadium compounds of the formula (4) (VX₄) are known and readilyavailable.

In the formula (5), M represents lithium, sodium, potassium, rubidium orcesium. Among them, lithium, sodium and potassium are preferred, andlithium and sodium are more preferred. In the formula (5), Cp representscyclopentadienyl, substituted cyclopentadienyl, indenyl, substitutedindenyl, fluorenyl, substituted fluorenyl, benzoindenyl, substitutedbenzoindenyl, azulenyl or substituted azulenyl. As the Cp groups, thegroups constituting the contemplated vanadocene compound (Cp₂VX₂) may beselected.

When two Cp groups in the contemplated vanadocene compound (Cp₂VX₂) aredifferent from each other, two kinds of alkali metal compounds (CpM)having different Cp groups are used as mixed.

The alkali metal compounds represented by the formula (5) (CpM) areknown and readily available.

The method of reaction between the vanadium compound (VX₄) and thealkali metal compound (CpM) is not limited. For example, the twocompounds can be reacted by mixing a solution or a slurry of thevanadium compound (VX₄) and a solution or a slurry of the alkali metalcompound (CpM), and stirring the resulting mixture.

In the reaction between the vanadium compound and alkali metal compound,there are no particular limitations on the reaction conditions e.g., thesolvent to be used, concentration of each compound, molar ratio ofvanadium compound/alkali metal compound, reaction temperature, reactiontime, and the like. The reaction conditions can be suitably determinedaccording to the desired product.

A variety of solvents can be used for dissolving or suspending thevanadium compound (VX₄) and the alkali metal compound (CpM). Among them,ethers and hydrocarbons are preferred. Specific examples of the solventto be used are ethyl ether, butyl methyl ether, sec-butyl methyl ether,t-butyl methyl ether, t-amyl methyl ether, butyl ethyl ether, sec-butylethyl ether, t-butyl ethyl ether, propyl ether, iso-propyl ether,tetrahydrofuran, 2-methyl tetrahydrofuran, 2,5-dimethyl tetrahydrofuran,1,3-dioxane, 1,4-dioxane, 4-methyl-1,3-dioxane, 1,3-dioxepane, toluene,xylene, hexane, heptane, octane, nonane, decane, etc. In the invention,ethyl ether and tetrahydrofuran are preferred.

The alkali metal compound (CpM) and the vanadium compound (VX₄) to beused as the raw materials are used, each in a concentration ofpreferably about 0.1 to about 3 moles/liter, more preferably about 0.2to about 2 moles/liter. When the alkali metal compound (CpM) and thevanadium compound (VX₄) are used in the above-mentioned concentrationrange, the reaction easily proceeds and unreacted substances remain in alesser amount or scarcely remain.

The alkali metal compound and the vanadium compound are used in a molarratio (CpM/VX₄) of preferably about 0.5 to about 5, more preferablyabout 1.5 to about 3. Since the theoretical molar ratio of the alkalimetal compound (CpM) to the vanadium compound (VX₄) is 2:1, thecontemplated vanadocene compound (Cp₂VX₂) can be prepared with a highpurity in a high yield by using the two compounds in the above-mentionedmolar ratio.

The reaction temperature is in the range of preferably about −100 toabout 100° C., more preferably about −50 to about 50° C. The reactiontime is in the range of preferably about 1 to about 100 hours, morepreferably about 2 to about 48 hours. When the reaction proceeds at saidtemperature, the reaction is unlikely to require excessively a prolongedtime, and the purity of obtained vanadocene compound is unlikely to belowered due to the production of by-products or decomposition of thevanadocene compound.

The foregoing reaction may be performed under atmospheric pressure, butpreferably carried out under a pressure of about 5×10⁴ to about 2×10⁵Pa.

The produced vanadocene compound (Cp₂VX₂) can be obtained by separationof insoluble solids precipitated from the reaction mixture throughfiltration or by evaporation of reaction mixture to dryness.

Chlorination of the Vanadocene Compound (Cp₂VX₂)

Description is given below on the method of reacting the vanadocenecompound (Cp₂VX₂) with chlorine gas.

When the vanadocene compound (Cp₂VX₂) is reacted with chlorine gas withaddition of oxygen and/or water to the reaction system, ahalf-vanadocene compound (CpVOCl₂) is produced. When the vanadocenecompound is reacted with chlorine gas without addition of oxygen orwater to the reaction system, a half-vanadocene compound (CpVCl₃) isproduced.

The method of reacting the vanadocene compound (Cp₂VX₂) with chlorinegas is not limited. For example, the vanadocene compound (Cp₂VX₂) can bereacted with chlorine gas by supplying chlorine gas to a solution or aslurry of vanadocene compound (Cp₂VX₂).

When the vanadocene compound (Cp₂VX₂) is reacted with chlorine gas inthe absence of oxygen and water, the reaction may be carried out underan atmosphere of inert gas such as rare gas or nitrogen gas.

When oxygen and/or water is mixed with the reaction system, chlorine gascan be supplied while continuously supplying oxygen and/or water to asolution or a slurry of the vanadocene compound (CP₂VX₂).

In the chlorination reaction of the vanadocene compound, there are noparticular limitations on reaction conditions, such as the solvent to beused, concentration of vanadocene compound (Cp₂VX₂), molar ratio ofvanadocene compound/chlorine (Cp₂VX₂/Cl₂), pressure of chlorine gas,reaction temperature, reaction time, molar ratio of vanadocenecompound/oxygen (Cp₂VX₂)/O₂) and molar ratio of vanadocenecompound/water (Cp₂VX₂)/H₂O) when the reaction is carried out in thepresence of oxygen and/or water. These reaction conditions can besuitably determined according to the desired product.

Useful solvents include organic solvents which are inert to thechlorination reaction of the invention, preferably halogenatedhydrocarbons or hydrocarbons. Examples of solvents are carbontetrachloride, chloroform, methylene chloride, 1,2-dichloroethane,1,1,1-trichloroethane, 1,1,2-trichloroethane, 1,1,1,2-tetrachloroethane,1,1,2,2-tetrachloroethane, bromoform, dibromoethane, 1,2-dibromoethane,1,1,2,2-tetrabromoethane and like halogenated hydrocarbons containing 1to 4 halogen atoms and 1 to 4 carbon atoms; pentane, hexane, heptane,octane, nonane, decane and like hydrocarbons having 5 to 12 carbonatoms; etc. Among them, halogenated hydrocarbons are preferred, andchloroform and methylene chloride are more preferred.

The vanadocene compound (Cp₂VX₂) is used in a concentration ofpreferably about 0.02 to about 2 moles/liter, more preferably about 0.1to about 1 mole/liter. When the concentration of the vanadocene compound(Cp₂VX₂) is in the foregoing range, the reaction easily proceeds, andunreacted substances remain in a lesser amount or scarcely remain.

The molar ratio of vanadocene compound/chlorine (Cp₂VX₂/Cl₂) ispreferably 0.5 to about 20, more preferably about 1 to about 10. Whenthe molar ratio of vanadocene compound/chlorine (Cp₂VX₂/Cl₂) is in theabove-mentioned range, the contemplated compound can be efficientlyproduced in a high yield.

The method of supplying chlorine gas is not limited. For example,chlorine gas may be continuously supplied until the foregoing molarratio is attained as a whole. Alternatively the required amount ofchlorine gas may be supplied at one time. The pressure of chlorine gasin the reaction is preferably about 0.02 to about 2 MPa, more preferablyabout 0.05 to about 1 MPa.

The reaction temperature is in the range of preferably about −50 toabout 150° C., more preferably about 0 to about 100° C. The reactiontime is in the range of preferably about 30 minutes to about 48 hours,more preferably about 1 to about 24 hours.

When the vanadocene compound (Cp₂VX₂) is reacted with chlorine gas inthe presence of oxygen, the molar ratio of vanadocene compound/oxygen(Cp₂VX₂/O₂) is preferably about 0.05 to about 2, more preferably about0.1 to about 1. When the vanadocene compound (CP₂VX₂) is reacted withchlorine gas in the presence of water, the molar ratio of vanadocenecompound/water (Cp₂VX₂/H₂O) is preferably about 0.1 to about 4, morepreferably about 0.2 to about 2. When the vanadocene compound (Cp₂VX₂)is reacted with chlorine gas in the presence of oxygen and water, themolar ratio of vanadocene compound/oxygen (Cp₂VX₂/O₂) is preferablyabout 0.05 to about 2, more preferably about 0.1 to about 1, and themolar ratio of vanadocene compound/water (Cp₂VX₂/H₂O) is preferablyabout 0.1 to about 4, more preferably about 0.2 to about 2.

After completion of chlorination of the vanadocene compound(Cp₂VX₂),usually the reaction solvent may be evaporated to dryness. By dissolvingthe resulting product, CpVOCl₂ or CpVCl₃, in a solvent, concentratingthe solution, cooling the concentrate, and carrying outrecrystallization, CpVOCl₂ or CpVCl₃ of high purity can be obtained. Therecrystallization can remove the impurities such as alkali metal salt(MX). Solvents useful for dissolving CpVOCl₂ or CpVCl₃ are, for example,benzene, toluene, xylene and like hydrocarbons, chloroform, methylenechloride and like halogenated hydrocarbons.

EXAMPLES

The present invention will be described in more detail with reference tothe following examples and test examples to which, however, theinvention is not limited.

Example 1

(a) Production of Vanadocene Compound

Vanadium tetrachloride (2.3 kg) was dissolved at −10° C. in 20 liters oftetrahydrofuran. While maintaining the solution at −10° C., 27 liters ofa solution of (C₅H₅)Na in tetrahydrofuran (conc. 0.88 mole/liter) wasadded dropwise over 4 hours. Solid was increasingly precipitated as(C₅H₅)Na was added dropwise. While stirring the resulting suspension,the temperature was elevated to 50° C. over 16 hours. While maintainingthe temperature at 50° C., tetrahydrofuran was evaporated under reducedpressure and the residue was vacuum-dried for 3 hours, giving 5.1 kg ofvanadocene compound as grayish-green solid. Analysis demonstrated thatthe solid contained 2.27 moles/kg of (C₅H₅)₂VCl₂.

(b) Chlorination

300 g of the obtained vanadocene compound was suspended in 2 liters ofchloroform and the suspension was heated to 50° C. Chlorine gas wasintroduced (gas flow rate: 3.6 liters/hr), and simultaneously 7.5milliliters of water was continuously added over 9 hours to conductchlorination. While maintaining the temperature at 50° C., chloroformwas evaporated under reduced pressure. The dry solid was washed threetimes with 1 liter of hexane. While the temperature of the residue wasmaintained at 50° C., the residue was washed twice with 1 liter oftoluene. The toluene filtrates were combined and concentrated.Recrystallization gave 83 g (yield 60%) of (C₅H₅)VOCl₂.

Example 2

(a) Production of Vanadocene Compound

The vanadocene compound, (C₅H₅)₂VCl₂, was prepared in the same manner asin Example 1(a).

(b) Chlorination

150 g of the obtained vanadocene compound was suspended in 1 liter ofchloroform and the suspension was heated to 50° C. Chlorine gas (gasflow 2 liters/hr) and oxygen gas (gas flow 0.6 liter/hr) werecontinuously supplied for 8 hours to conduct chlorination. Afterchlorination, the same work-up procedure as done in Example 1(b) wascarried out, giving 40 g of (C₅H₅)VOCl₂ (yield 58%).

Example 3

The same procedure as in Example 1 was conducted except that hexane wasused as the solvent in the chlorination reaction, giving (C₅H₅)VOCl₂.

Example 4

(a) Production of Vanadocene Compound

Vanadium tetrachloride (38 g) was dissolved in 400 milliliters oftetrahydrofuran cooled to −20° C. The temperature of the solution roseto −10° C. While retaining the temperature of the solution at −10° C.,440 milliliters of a tetrahydrofuran solution of (C₅H₄CH₃)Li(concentration 0.92 mole/liter) was added dropwise over 3 hours. Thetemperature of the obtained suspension was elevated to room temperatureover 24 hours while it was stirred. The tetrahydrofuran was evaporatedunder reduced pressure while retaining the temperature at 50° C. Theresidue was vacuum-dried for 3 hours, thereby giving a vanadocenecompound, (C₅H₄ CH₃)₂VCl₂, as a dry solid.

(b) Chlorination

400 milliliters of chloroform was added to the dry solid of thevanadocene compound to give a suspension. While maintaining thetemperature at 50° C., 2.2 milliliters of water was continuously addedover 9 hours simultaneously with introduction of chlorine gas (gas flowrate: 0.95 liter/hr) to conduct chlorination. While maintaining thetemperature at 50° C. after completion of chlorination reaction, thechloroform was evaporated under reduced pressure. The dry solid waswashed twice with 200 milliliters of hexane. While the temperature ofthe residue was maintained at 50° C., the residue was washed twice with500 milliliters of toluene. The toluene filtrates were combined andconcentrated. Recrystallization gave 19 g (yield 44%) of (C₅H₄CH₃)VOCl₂.

Example 5

(a) Production of Vanadocene Compound

The vanadocene compound, (C₅H₅)₂VCl₂, was prepared in the same manner asin Example 1, (a).

(b) Chlorination

150 g of the obtained vanadocene compound was suspended in 1 liter ofchloroform. Then the suspension was heated to 50° C. Chlorine gas (gasflow rate: 1.1 liters/hr) was continuously supplied for 9 hours toconduct chlorination reaction. While maintaining the temperature at 50°C., the chloroform was evaporated under reduced pressure. The dry solid(final product) was washed twice with 1 liter of hexane. While thetemperature of the residue was maintained at 50° C., the residue waswashed three times with 1 liter of toluene. The toluene filtrates werecombined and concentrated. Recrystallization gave 39 g (yield 52%) of(C₅H₅)VCl₃.

Comparative Example 1

100 g of (C₅H₅)₂VCl₂ was suspended in 300 milliliters of chloroform. Thesuspension was cooled to 0° C. 300 milliliters of SOCl₂ as achlorinating agent was added to the suspension. Thereby the temperatureof the solution rose to 15° C. While maintaining the temperature at 30°C., oxygen (gas flow 0.6 liter/hr) was continuously supplied for 9hours. After completion of chlorination, the chloroform and SOCl₂ wereevaporated under reduced pressure while maintaining the temperature at50° C. After washing the dry solid (final product) with hexane, it waswashed three times with 0.5 liter of toluene. The toluene filtrates werecombined and concentrated. Recrystallization gave 17 g of (C₅H₅)VOCl₂(yield 21%).

Comparative Example 2

600 milliliters of SOCl₂ was cooled to 0° C. and 100 g of (C₅H₅)₂VCl₂was added to obtain a suspension. Thereby the temperature of thesuspension rose to 10° C. While maintaining the temperature at 30° C.,chlorination reaction was conducted for 9 hours. After completion ofchlorination reaction, the chloroform and SOCl₂ were evaporated underreduced pressure while maintaining the temperature at 50° C. Afterwashing the final product (solid evaporated to dryness) with hexane, thesolid was washed three times with 0.5 liter of toluene. The toluenefiltrates were combined and concentrated. Recrystallization gave 16 g of(C₅H₅)VCl₃ (yield 18%).

The half-vanadocene compounds prepared in Examples 1 to 5 were found tohave a purity of 99% or higher according to titrimetric analysis. Thehalf-vanadocene compounds of Examples 1 to 5 were produced in a yield of44 to 60%, which were higher than yields of about 20% in ComparativeExamples 1 and 2 illustrative of the results of prior art processes.This means that according to the process of the present invention, ahalf-vanadocene compounds can be produced with a high purity in a highyield.

1. A process for preparing a half-vanadocene compound, the processcomprising reacting chlorine gas with a vanadocene compound representedby the formula (1) in the presence of at least one member selected fromthe group consisting of oxygen and water,CP₂VX₂  (1) wherein Cp represents cyclopentadienyl, substitutedcyclopentadienyl, indenyl, substituted indenyl, fluorenyl, substitutedfluorenyl, benzoindenyl, substituted benzoindenyl, azulenyl orsubstituted azulenyl, and the two Cp groups may be the same ordifferent, X represents fluorine, chlorine, bromine or iodine and thetwo X atoms may be the same or different.
 2. A process for preparing ahalf-vanadocene compound according to claim 1, wherein Cp representscyclopentadienyl; cyclopentadienyl having 1 to 5 substituents selectedfrom the group consisting of hydrocarbon groups having 1 to 20 carbonatoms and silicon-containing hydrocarbon groups having 1 to 20 carbonatoms; indenyl; indenyl having 1 to 6 substituents selected from thegroup consisting of hydrocarbon groups having 1 to 20 carbon atoms andsilicon-containing hydrocarbon groups having 1 to 20 carbon atoms;fluorenyl; fluorenyl having 1 to 8 substituents selected from the groupconsisting of hydrocarbon groups having 1 to 20 carbon atoms andsilicon-containing hydrocarbon groups having 1 to 20 carbon atoms;benzoindenyl; benzoindenyl having 1 to 8 substituents selected from thegroup consisting of hydrocarbon groups having 1 to 20 carbon atoms andsilicon-containing hydrocarbon groups having 1 to 20 carbon atoms;azulenyl; or azulenyl having 1 to 7 substituents selected from the groupconsisting of hydrocarbon groups having 1 to 20 carbon atoms andsilicon-containing hydrocarbon groups having 1 to 20 carbon atoms, andthe two C_(p) groups may be the same or different.
 3. A process forpreparing a half-vanadocene compound according to claim 1, wherein Cprepresents cyclopentadienyl; cyclopentadienyl having 1 to 5 substituentsselected from the group consisting of methyl, ethyl, n-propyl,iso-propyl, n-butyl, iso-butyl, sec-butyl, t-butyl and phenyl; indenyl;indenyl having 1 to 6 substituents selected from the group consisting ofmethyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, sec-butyl,t-butyl and phenyl; fluorenyl; fluorenyl having 1 to 8 substituentsselected from the group consisting of methyl, ethyl, n-propyl,iso-propyl, n-butyl, iso-butyl, sec-butyl, t-butyl and phenyl;benzoindenyl; benzoindenyl having 1 to 8 substituents selected from thegroup consisting of methyl, ethyl, n-propyl, iso-propyl, n-butyl,iso-butyl, sec-butyl, t-butyl and phenyl; benzoindenyl; benzoindenylhaving 1 to 8 substituents selected from the group consisting of methyl,ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, sec-butyl, t-butyl andphenyl; azulenyl; or azulenyl having 1 to 7 substituents selected fromthe group consisting of methyl, ethyl, n-propyl, iso-propyl, n-butyl,iso-butyl, sec-butyl, t-butyl and phenyl, and the two Cp groups may bethe same or different.
 4. The process for preparing a half-vanadocenecompound according to claim 1, wherein the compound represented by theformula (1) is selected from the group consisting of (C₅H₅)₂VF₂,(C₅H₅)₂, VCl₂, (C₅H₅)₂VBr₂, (C₅H₅)₂VI₂, (CH₃C₅H₄)₂VF₂, (CH₃C₅H₄)₂VCl₂,(CH₃C₅H₄)₂VBr₂, (CH₃C₅H₄)₂VI₂, [1,2-(CH₃)₂C₅H₃]₂VF₂,[1,2-(CH₃)₂C₅H₃]₂VCl₂, [1,2-(CH₃)₂C₅H₃]₂VBr₂, [1,2-CH₃ ₂C₅H₃]₂VI₂,[1,3-(CH₃)₂C₅H₃]₂VF₂, [1,3-(CH₃)₂C₅H₃]₂VCl₂, [1,3-(CH₃)₂C₅H₃]₂VBr₂,[1,3-(CH₃)₂C₅H₃]₂VI₂, [1,2,3-(CH₃)₃C₅H₂]₂VF₂, [1,2,3-(CH₃)₃C₅H₂]₂VCl₂,[1,2,3-(CH₃)₃C₅H₂]₂VBr₂, [1,2,3-(CH₃)₃C₅H₂]₂VI₂, [1,2,4-(CH₃)₃C₅H₂]₂VF₂,[1,2,4-(CH₃)₃C₅H₂]₂VCl₂, [1,2,4-(CH₃)₃C₅H₂]₂VBr₂,[1,2,4-(CH₃)₃C₅H₂]₂VI₂, [(CH₃)₄C₅H]₂VF₂, [(CH₃)₄C₅H]₂VCl₂,[(CH₃)₄C₅H]₂VBr₂, [(CH₃)₄C₅H]₂VI₂, [(CH₃)₅C₅]₂VF₂, [(CH₃)₅C₅]₂VCl₂,[(CH₃)₅C₅]₂VBr₂, [(CH₃)₅C₅]₂VI₂, (1-CH₃-2-C₂H₅C₅H₃)₂VF₂,(1-CH₃-2-C₂H₅C₅H₃ ₂VCl₂, (1-CH₃-C₂H₅C₅H₃)₂VBr₂, (1-CH₃-2-C₂H₅C₅H₃)₂VI₂,1-CH₃-3-C₂H₅C₅H₃)₂VF₂, (1-CH₃-3-C₂H₅C₅H₃)₂VCl₂, (1-CH₃-3-C₂H₅C₅H₃)₂VBr₂,(1-CH₃-3-C₂H₅C₅H₃)₂VI₂, (1-CH₃-2-n-C₃H₇C₅H₃)₂VF₂,(1-CH₃-2-n-C₃H₇C₅H₃)₂VCl₂, (1-CH₃-2-n-C₃H₇C₅H₃)₃ ₂VBr₂,(1-CH₃-2-n-C₃H₇C₅H₃)₂VI₂, (1-CH₃-2-iso-C₃H₇C₅H₃)₂VF₂,(1-CH₃-2-iso-C₃H₇C₅H₃)₂VCl₂, (1-CH₃-2-iso-C₃H₇C₅H₃)₂VBr₂,(1-CH₃-2-iso-C₃H₇C₅H₃)₂VI₂, (1-CH₃-3-n-C₃H₇C₅H₃)₂VF₂,(1-CH₃-3-n-C₃H₇C₅H₃), ₂VCl₂, (1-CH₃-3-n-C₃H₇C₅H₃)₂VBr₂,(1-CH₃-3-n-C₃H₇C₅H₃)₂VI₂, (1-CH₃-3-iso-C₃H₇C₅H₃)₂VF₂,(1-CH₃-3-iso-C₃H₇C₅H₃)₂Cl₂, (1-CH₃3-iso-C₃H₇C₅H₃)₂VBr₂,(1-CH₃-iso-C₃H₇C₅H₃)₂VI₂, (C₂H₅C₅H₄)₂VF₂, (C₂H₅C₅H₄)₂VCl₂, (C₂H₅C₅₄)₂VBr₂, (C₂H₅C₅H₄)₂VI₂, [1,2-(C₂H₅)₂C₅H₃]₂VF₂, [1,2-(C₂H₅)₂C₅H₃]₂VCl₂,[1,2-(C₂H₅)₂C₅H₃]₂VBr₂, [1,2-(C₂H₅)₂C₅H₃]₂VI₂, [1,3-(C₂H₅)₂C₅H₃]₂VF₂,[1,3-(C₂H₅)₂C₅H₃]₂VCl₂, [1,3-(C₂H₅)₂C₅H₃]₂VBr₂, [1,3-(C₂H₅)₂C₅H₃]₂VI₂,[1,2-(n-C₃H₇)₂C₅H₃]₂, VF₂, [1,2-(n-C₃H₇)₂C₅H₃]₂VCl₂,[1,2-(n-C₃H₇)₂C₅H₃]₂VBr₂, [1,2-(n-C₃H₇)₂C₅H₃]₂VI₂,[1,3-(n-C₃H₇)₂C₅H₃]₂VF₂, [1,3-(n-C₃H₇)₂C₅H₃]₂VCI₂,[1,3-(n-C₃H₇)₂C₅H₃]₂VBr₂, [1,3-(n-C₃H₇)₂C₅H₃]₂VI₂,[1,2-(iso-C₃H₇)₂C₅H₃]₂VF₂, [1,2-(iso-C₃H₇)₂C₅H₃]₂VCI₂,[1,2-(iso-C₃H₇)₂C₅H₃]₂VBr₂, [1,2-(iso-C₃H₇)₂C₅H₃]₂VI₂,[1,3-(iso-C₃H₇)₂C₅H₃]₂VF₂, [1,3-(iso-C₃H₇)₂C₅H₃]₂VCI₂,[1,3-(iso-C₃H₇)₂C₅H₃]₂VBr₂, [1,3-(iso-C₃H₇)₂C₅H₃]₂VI₂,[1,2-(n-C₄H₉)₂C₅H₃]₂VF₂, [1,2-(n-C₄H₉)₂C₅H₃]₂VCI₂,1,2-(n-C₄H₉)₂C₅H₃]₂VBr₂, [1,2-(n-C₄H₉)₂C₅H₃]₂VI₂,[1,3-(n-C₄H₉)₂C₅H₃]₂VF₂, [1,3-(n-C₄H₉)₂C₅H₃]₂VCI₂,[1,3-(n-C₄H₉)₂C₅H₃]₂VBr₂, [1,3-(n-C₄H₉)₂C₅H₃]₂VBr₂,[1,3-(t-C₄H₉)₂C₅H₃]₂VI₂, (n-C₅H₁₁C₅H₄)₂VF₂, (n-C₅H₁₁C₅H₄)₂VCI₂,(n-C₅H₁₁C₅H₄)₂VBr₂, (n-C₅H₁₁C₅H₄)₂VI₂, (n-C₆H₁₃C₅H₄)₂VF₂,(n-C₆H₁₃C₅H₄)₂VCI₂, (n-C₆H₁₃C₅H₄)₂VBr₂, (n-C₆H₁₃C₅H₄)₂VI₂,(n-C₈H₁₇C₅H₄)₂VF₂, (n-C₈H₁₇C₅H₄)₂VCI₂, (n-C₈H₁₇C₅H₄)₂VBr₂,(n-C₈H₁₇C₅H₄)₂VI₂, (C₆H₅C₅H₄)₂VF₂, (C₆H₅C₅H₄)₂VCI₂, (C₆H₅C₅H₄)₂VBr₂,(C₆H₅C₅H₄)₂VI₂, (C₆H₅CH₂C₅H₄)₂VF₂, (C₆H₅CH₂C₅H₄)₂VCI₂,(C₆H₅CH₂C₅H₄)₂VBr₂, (C₆H₅CH₂C₅H₄)₂VI₂, [(CH₃)₃SiC₅H₄]₂, VF₂,[(CH₃)₃SiC₅H₄]₂VCI₂, [(CH₃)₃SiC₅H₄]₂VBr₂, [(CH₃)₃SiC₅H₄]₂VI₂,{1,3-[(CH₃)₃Si]₂C₅H₃}₂VF₂, {1,3-[(CH₃)₃Si]₂C₅H₃}₂VCI₂,{1,3-[(CH₃)₃Si]₂C₅H₃}₂VBr₂, {1,3-[(CH₃)₃Si]₂C₅H₃}₂VI₂,[(CH₃)₉Si(CH₃)C₅H₃]₂VF₂, [1-(CH₃)₃Si-3-CH₃C₅H₃]₂VCI₂,[1-(CH₃)₃Si-3-CH₃C₅H₃]₂VBr₂, [1-(CH₃)₃Si-3-CH₃C₅H₃]₂VI₂,{1,3-[(CH₃)₃Si]₂-4-CH₃C₅H₂}₂VF₂, {1,3-[(CH₃)₃Si]₂-4-CH₃C₅H₂}₂VCI₂,{1,3-[(CH₃)₃Si]₂-4-CH₃C₅H₂}₂VBr₂, {1,3-[(CH₃)₃Si]₂-4-CH₃C₅H₂}₂VI₂,Ind₂VF₂, Ind₂VCl₂, Ind₂VBr₂, Ind₂VI₂, (2-CH₃Ind)₂VF₂, (2-CH₃Ind), ₂VCl₂,(2-CH₃Ind)₂VBr₂, (2-CH₃Ind)₂VI₂, (2-C₂H₅Ind)₂VF₂, (2-C₂H₅Ind)₂VCI₂,(2-C₂H₅Ind)₂VBr₂, (2-C₂H₅Ind)₂VI₂, (2-n-C₃H₇Ind)₂VF₂,(2-n-C₃H₇Ind)₂VCl₂, (2-n-C₃H₇Ind)₂VBr₂, (2-n-C₃H₇Ind), ₂VI₂,(2-iso-C₃H₇Ind)₂VF₂, (2-iso-C₃H₇Ind)₂VCI₂, (2-iso-C₃H₇Ind)₂VBr₂,(2-iso-C₃H₇Ind)₂VI₂, (2-n-C₄H₉Ind)₂VF₂, (2-n-C₄H₉Ind)₂VCI₂,(2-n-C₄H₉Ind)₂VBr₂, (2-n-C₄H₉Ind)₂VI₂, (2-t-C₄H₉Ind)₂VF₂,(2-t-C₄H₉Ind)₂VCI₂, (2-t-C₄H₉Ind)₂VBr₂, (2-t-C₄H₉Ind)₂VI₂,[2-(CH₃)₃SiInd)]₂VF₂, [2-(CH₃)₃SiInd)]₂VCI₂, [2-(CH₃)₃SiInd)]₂VBr₂,[2-(CH₃)₃SiInd)]₂VI₂, [2,4-(CH₃)₂Ind)]₂VF₂, [2,4-(CH₃)₂Ind)]₂VCI₂,[2,4-(CH₃)₂Ind)]₂VBr₂, [2,4-(CH₃)₂Ind)]₂VI₂, [2-(CH₃)-4-C₆H₅Ind)]₂VF₂,[2-CH₃-4-C₆H₅Ind)]₂VCI₂, [2-CH₃)-4-C₆H₅Ind)]₂VBr₂,[2-(CH₃)-4-C₆H₅Ind)]₂VI₂, (H₄Ind)₂VF₂, (H₄Ind)₂VCI₂, (H₄Ind)₂VBr₂,(H₄Ind)₂VI₂, Flu₂VF₂, Flu₂VCI₂, Flu₂VBr₂, Flu₂VI₂, (9-CH₃Flu)₂VF₂,(9-CH₃Flu)₂VCl₂, (9-CH₃Flu)₂VBr₂, (9-CH₃Flu)₂VI₂, (9-C₂H₅Flu)₂VF₂,(9-C₂H₅Flu)₂VCI₂, (9-C₂H₅Flu)₂VBr₂, (9-C₂H₅Flu)₂VI₂, (9-n-C₃H₇Flu)₂VF₂,(9-n-C₃H₇Flu)₂VCI₂, (9-n-C₃H₇Flu)₂VBr₂, (9-n-C₃H₇Flu)₂VI₂,(9-iso-C₃H₇Flu)₂VF₂, (9-iso-C₃H₇Flu)₂VCI₂, (9-iso-C₃H₇Flu)₂VBr₂,(9-iso-C₃H₇Flu)₂VI₂, (9-n-C₄H₉Flu)₂VF₂, (9-n-C₄H₉Flu)₂VCI₂,(9-n-C₄H₉Flu)₂VBr₂, (9-n-C₄H₉Flu)₂VI₂, [1,9-(CH₃)₂Flu)₂VF₂,[1,9-(CH₃)₂Flu)₂VCI₂, [1,9-(CH₃)₂Flu]₂VBr₂, [1,9-(CH₃)₂Flu]₂VI₂,(H₈Flu)₂VF₂, (H₈Flu)₂VCI₂, (H₈Flu)₂VBr₂, (H₈Flu)₂VI₂, (Bind₂VF₂),(Bind₂VCl₂), (Bind₂VBr₂), (Bind₂VI₂), (2-CH₃Bind)₂VF₂, (2-CH₃Bind)₂VCl₂,(2-CH₃Bind)₂VBr₂, (2-CH₃Bind)₂VI₂, (2-C₂H₅Bind)₂VF₂, (2-C₂H₅Bind)₂VCI₂,(2-C₂H₅Bind)₂VBr₂, (2-C₂H₅Bind)₂VI₂, (2-n-C₃H₇Bind)₂VF₂,(2-n-C₃H₇Bind)₂VCI₂, (2-n-C₃H₇Bind)₂VBr₂, (2-n-C₃H₇Bind)₂VI₂,(2-iso-C₃H₇Bind)₂VF₂, (2-iso-C₃H₇Bind)₂VCI₂, (2-iso-C₃H₇Bind)₂VBr₂,(2-iso-C₃H₇Bind)₂VI₂, (2-n-C₄H₉Bind)₂VF₂, (2-n-C₄H₉Bind)₂VCI₂,(2-n-C₄H₉Bind)₂VBr₂, (2-n-C₄H₉Bind)₂VI₂, (2-t-C₄H₉Bind)₂VF₂,(2-t-C₄H₉Bind)₂VCI₂, (2-t-C₄H₉Bind)₂VBr₂, (2-t-C₄H₉Bind)₂VI₂, Azu₂VF₂,Azu₂VCl₂, Azu₂VBr₂, Azu₂VI₂, (2-CH₃Azu)₂VF₂, (2-CH₃Azu)₂VCI₂,(2-CH₃AZU)₂VBr₂, (2-CH₃Azu)₂VI₂, (2-C₂H₅Azu)₂VF₂, (2-C₂H₅Azu)₂VCI₂,(2-C₂H₅Azu)₂VBr₂, (2-C₂H₅Azu)₂VI₂, (2-n-C₃H₇Azu)₂VF₂,(2-n-C₃H₇Azu)₂VCI₂, (2-n-C₃H₇Azu)₂VBr₂, (2-n-C₃H₇Azu)₂VI₂,(2-iso-C₃H₇Azu)₂VF₂, (2-iso-C₃H₇Azu)₂VCI₂, (2-iso-C₃H₇Azu)₂VBr₂,(2-iso-C₃H₇Azu)₂VI₂, (4,8-(CH₃)₂Azu)₂VF₂, (4,8-(CH₃)₂Azu)₂VCI₂,(4,8-(CH₃)₂Azu)₂VBr₂, (4,8-(CH₃)₂Azu)₂VI₂, (2,4,8-(CH₃)₃Azu)₂VF₂,(2,4,8-(CH₃)₃Azu)₂VCl₂, (2,4,8-(CH₃)₃Azu)₂Br₂, (2,4,8-(CH₃)₃Azu)₂VI₂,[2-iso-C₃H₇-4,8-(CH₃)₂Azu]₂VF₂, [2-iso-C₃H₇-4,8-(CH₃)₂Azu]₂VCl₂,[2-iso-C₃H₇-4,8-(CH₃)₂Azu]₂VBr₂, and [2-iso-C₃H₇-4,8-(CH₃)₂Azu]₂VI₂,wherein Ind represents indenyl, Flu represents fluorenyl, Bindrepresents benzoindenyl, Azu represents azylenyl, H₄Ind represents thefollowing group (6).

and H₈Flu represents the following group (7).


5. The process for preparing a half-vanadocene compound according toclaim 1, wherein the half-vanadocene compound to be obtained is acompound represented by the formula (3)CpVOCl₂  (3) wherein Cp represents cyclopentadienyl, substitutedcyclopentadienyl, indenyl, substituted indenyl, fluorenyl, substitutedfluorenyl, benzoindenyl, substituted benzoindenyl, azulenyl orsubstituted azulenyl.
 6. A process for preparing a half-vanadocenecompound, the process comprising reacting chlorine gas with a vanadocenecompound represented by the formula (1) in the presence of oxygen andwater,Cp₂VX₂  (1) wherein Cp represents cyclopentadienyl, substitutedcyclopentadienyl, indenyl, substituted indenyl, fluorenyl, substitutedfluorenyl, benzoindenyl, substituted benzoindenyl, azulenyl orsubstituted azulenyl, and the two Cp groups may be the same ordifferent, X represents fluorine, chlorine, bromine or iodine and thetwo X atoms may be the same or different.
 7. The process for preparing ahalf-vanadocene compound according to claim 6, wherein thehalf-vanadocene compound to be obtained is a compound represented by theformula (3)CpVOCl₂  (1) wherein Cp represents cyclopentadienyl, substitutedcyclopentadienyl, indenyl, substituted indenyl, fluorenyl, substitutedfluorenyl, benzoindenyl, substituted benzoindenyl, azulenyl orsubstituted azulenyl.